In a gas turbine engine, compressed air discharged from a compressor section is mixed with fuel and burned in a combustion section, creating combustion products comprising hot combustion gases. The combustion gases are directed through a hot gas path in a turbine section comprising a series of turbine stages typically including a plurality of paired rows of stationary vanes and rotating turbine blades. The turbine blades extract energy from the combustion gases and provide rotation of a turbine rotor for powering the compressor and providing output power.
The airfoils of the vanes and blades are typically exposed to high operating temperatures, and thus include cooling circuits to remove heat from the airfoil and to prolong the life of the vane and blade components. A portion of the compressed air discharged from the compressor section may be diverted to these cooling circuits. Manufacture of airfoils with one or more cooling circuits typically requires the use of a ceramic core comprising framing channels at the radially inner and outer portions in order to provide sufficient structural stability and to prevent unzipping of the ceramic core during casting.